1. Field of Invention
This invention relates to a heating apparatus that will heat a hybrid plastisol hot melt that is a flowable liquid at room temperature to a temperature wherein the material becomes molten at approximately 280° F. to 350° F. In addition, the device statically mixes the molten liquid converting it to a hot melt as it exits from the apparatus into commercially available hot melt dispensing heads. Once the molten material is dispensed, it has adhesive properties identical to packaging hot melt.
2. Description of Related Art
U.S. Patent Application Publication No. 2004/0029980 A1 describes a hybrid plastisol hot melt composition that is liquid at room temperature. The hybrid plastisol is comprised of various micron-size resins and chemicals suspended in a liquid carrier. When this liquid is heated and mixed, it becomes a 100 percent solid hot melt that produces fiber-tear bonds when it is compressed and cooled between two cellulosic substrates.
This liquid hybrid plastisol exists in three distinct physical states. At room temperature, it is a liquid. When it is heated from 150° F. to approximately 270° F., it becomes a solid. When it is heated to approximately 280° F. and above, it becomes a molten liquid. When this molten liquid is mixed, it becomes a molten hot melt.
In order for this hybrid plastisol to be useful as a hot melt, it must be pumped under pressure through a device that heats the material to its molten temperature state and mixes its discrete molten ingredients to become a homogenous blend and be supplied under pressure to a manual or automatic dispenser. Unfortunately, before the hybrid plastisol reaches its melting point, it must pass through a temperature range between 150° F. and 270° F. during which it is a solid.
There are difficult challenges to overcome in order to elevate the temperature of this material from its liquid state at room temperature to its molten state at approximately 280° F. and above.
One specific problem to overcome is that between its room temperature liquid state and molten state at +300° F., the material is an un-pumpable solid. Therefore, an apparatus had to be developed that would minimize the volume of material existing in its solid state so that it could flow through supply hoses and piping via plug flow.
One method to achieve a minimal volume solid zone is to direct cooling compressed air at the supply piping feeding the heat exchanger. Heat migrating is mitigated by a 3 to 5 cfm air nozzle directed at the pipe nipple. The result is that the portion of material at its solid state is only 50 to 100 cc's within the pipe nipple, so it is easily forced into the heat exchanger by plug flow hydraulic pressure from the liquid contacting the solid plug.
One major disadvantage to the above is the requirement for compressed air which is a very expensive utility that would have to be supplied to multiple heat exchangers in a manufacturing environment. A further disadvantage is if plant air availability is interrupted for any reason heat will migrate from the ⅛ inch supply nipple into the supply hose causing material to solidify in the pipe and hose in sufficient volume that it cannot be moved by hydraulic pressure; therefore, material supply is stopped.
The present invention is a combination heat exchanger heat dissipater that minimizes the volume of material held at its solid phase temperature range of 150° F. to 270° F. The heat dissipater is static and does not require the use of compressed air.
The heat exchanger combination performs three functions simultaneously, heat the incoming material to its melting temperature, statically mix the molten material as it exits from the heat exchanger and statically dissipate thermal energy so that it does not migrate into the room temperature supply hose; thus minimizing the volume of material held at its solid phase temperature range of 150° F. to 270° F.